The two specific goals of this project are to understand how the taste of salt is processed in multiple brain regions, and to understand how this processing changes when sodium need changes. Work towards both of these goals will advance our current understanding of basic taste processing. To accomplish the first goal, taste-responsive neurons in two brain regions known to be involved in the perception of sodium taste (primary taste cortex and the central nucleus of the amygdala) will be simultaneously recorded from awake rats receiving a range of taste solutions that vary in quality, concentration, and palatability. The responses of ensembles of neurons to each taste will be compared, in order to test current theories of how these regions may interact during the taste processing. To accomplish the second goal, this taste-evoked activity in normal rats will be compared to that in rats that have undergoing rapid sodium depletion. These depletions reliably increase the palatability of NaCl, and should predictably shift the responses of neurons thought to be involved in sodium palatability coding. The results of this experiment will provide a robust test of current characterizations of taste processing in rats, and serve to dissociate processing that is a function of taste palatability from processing that is purely a function of taste intensity. PUBLIC HEALTH RELEVANCE: This project adds to our understanding of how interconnected brain regions transform the taste of sodium into a desire for sodium under different levels of sodium need. This basic knowledge is of general interest, as elevated sodium consumption can have negative implications for cardiovascular health. Further, understanding how an animal's internal-state influences sensory processing has far-reaching implications for understanding appetites and disorders of appetites.